<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .active{
            background: pink;
            width: 100px;
            height: 100px;
        }
    </style>
</head>
<body>
    <div id="app">
        <div :class="{ 'active': isActive }"></div>
    </div>
<script src="https://unpkg.com/vue@2.6.1/dist/vue.min.js"></script>
<script>
    var app = new Vue({
        el: '#app',
        data: {
            isActive: true
        }
    });
</script>
</body>
</html>